Jinwoo An

Sustainable Utilization of MSWI Bottom Ash as Road Construction Materials, Part I: Physical and Mechanical Evaluation

Current management practice, existing regulations, and environmental consequences of municipal solid waste incineration (MSWI) ash utilization were comprehensively reviewed. Efforts were made to physically and mechanically characterize MSWI bottom and fly ashes and also to evaluate their influence on the structural properties of Portland cement concrete (PCC) and hot-mix asphalt (HMA) when part of fine aggregate is replaced with the MSWI bottom ash. Fundamental properties of MSWI bottom ash and fly ash were studied by conducting physical, microstructural, and chemical tests. Concrete cylinders were cast with various amounts of ash additions and their strength and durability were investigated as the replacement ratio of ash increases. The MSWI bottom ash was also used to replace fine aggregate in HMA. Varying proportions of bottom ash and fine aggregate were tried in an effort to determine the optimum ratio of bottom ash to fine aggregate, as determined by performance tests such as the Marshall Stability and Flow test and the moisture susceptibility test.

Improvements to the structural condition index (SCI) for pavement structural evaluation at network level

Structural evaluation provides valuable information about the expected behaviour and response of pavements and can be used at the network level of pavement management to prioritise projects. The falling weight deflectometer (FWD) can be used to identify the beginning and end of management sections and group pavement sections with similar structural capacities. The structural condition index (SCI) was developed as a screening tool for the pavement network-level evaluation, and the FWD data are used to determine the SCI. For the successful implementation of the SCI concept at the network level, one of the critical issues is the accuracy of the index. This article evaluates the accuracy of the SCI and also discusses a concept and procedure how to improve the SCI and its algorithm for low-volume flexible pavements. A case study (Texas) illustrates that the original SCI algorithm underestimates the existing structural condition, resulting in overestimated treatments in the pavement maintenance and rehabilitation.

An optimum selection strategy of reflective cracking mitigation methods for an asphalt concrete overlay over flexible pavements

Abstract Reflective Cracking (RC) has been a daunting challenge in pavement maintenance and rehabilitation (M&R), yet, still, after several decades of research, no exclusive solution prevails. Moreover, RC mitigation methods have shown significant variation in in situ performance. Therefore, a technique tailored to select an effective RC mitigation method is essential for the success of pavement M&R. In this study, a life cycle cost (LCC) and multi-criteria decision-making (MCDM) analyses were conducted to evaluate the effectiveness of currently available RC mitigation methods and to select the optimal method for an asphalt concrete overlay above flexible pavements. The MCDM includes three components: LCC, performance, and materials (recyclability). These criteria determine the selection ranking of each RC mitigation method. In addition, the effects of the priority level including cost, performance, and recyclability on the final decision were evaluated by conducting a series of sensitivity analysis under multiple scenarios; therefore, weight combination of the three criteria were recorded to define the measurements affecting the final decision.

Improvements to the AASHTO Subgrade Resilient Modulus (M R ) Equation

Evaluation of subgrade soil stiffness provides valuable information about the expected behavior and response of pavements, which can be used to group pavement sections with similar structural capacities and pavement maintenance and rehabilitation to prioritize projects. A deflection test, such as the falling weight deflectometer (FWD), is commonly used to determine subgrade resilient modulus (MR) from its measured deflection data. A correction factor has been applied to the American Association of State Highway and Transportation Officials (AASHTO) MR equation for adjusting the difference between laboratory MR and the in situ measurements (with the FWD). However, large variations on the correction factor result in less accuracy of subgrade MR based on FWD measurements. The objective of this research is to evaluate the accuracy of the AASHTO MR equation and improve its accuracy by adjusting the MR correction factor. This paper consists of subtasks: (a) evaluating the current AASHTO MR correction factor; (b) evaluating the affecting factors (i.e., subgrade soil stiffness, bedrock depth, highway classification, and environmental condition); and (c) developing a framework to determine accurate MR correction factor.

Numerical Analysis of Reflective Cracking in an Asphalt Concrete Overlay over a Flexible Pavement

Previous studies have typically illustrated the three cracking mechanisms: (1) thermally induced fatigue due to a horizontal movement, (2) traffic induced fatigue due to vertical differential movement, and (3) surface initiated cracking due to the curling/warping of underlying slabs. Although these mechanisms are commonly observable for asphalt concrete overlay over both flexible and rigid pavements, the behavior and response of asphalt concrete (AC) overlay over a flexible pavement may be somewhat different from those over a rigid pavement due to their different characteristics of material and structure. Approximately 94% of 2.27 million miles of paved roads in the United States are overlaid with asphalt concrete. The mechanism of reflective cracking in AC overlays over flexible pavements has not been separately differentiated. Moreover, the bonding condition between AC overlays and flexible pavements is commonly assumed as bonded condition, although the interface condition can vary. This paper investigates the reflective cracking mechanism in an AC overlay over flexible pavements under different loading conditions by using a finite element (FE) analysis with bonded and unbonded conditions. The FE simulations also include partial top-down cracking conditions in the underlying flexible pavement. Deformed crack shapes and the highest stress concentration under traffic loading were investigated so that the initiation and propagation of reflective cracking are clearly understood.

A Review on the Effects of Earthborne Vibrations and the Mitigation Measures

Earthborne vibrations are induced by construction operation such as pile driving, roadbed compaction, and blasting and also by transit activities such as truck and trains. The earthborne vibration creates the stress waves traveling outward from the source and can structurally damage nearby buildings and structures in the forms of direct damage to structure and damage due to dynamic settlement. The wave propagation characteristics depends on impact or vibration energy, distance from the source, and soil characteristics. The aim of this paper is to provide a comprehensive review on the mechanistic of earthborne vibration and the current practice of vibration control and mitigation measures. The paper describes the state of knowledge in the areas of: (1) mechanics of earthborne vibration, (2) damage mechanism by earthborne vibration, (3) calculation, prediction of ground vibration, (4) the criteria of vibration limits, (5) vibration mitigation measures and their performance, and (6) the current practice of vibration control and mitigation measures.